Vitamin D prevents diabetes, improves insulin sensitivity: Study

In a report recently published in the British Journal of Nutrition, scientists from New Zealand’s Massey University studied 81 South Asian women between the ages of 23 and 68 who were all diagnosed with insulin resistance syndrome, also known as metabolic syndrome. This condition, which is linked to an increased risk of both diabetes and heart disease, describes a cluster of health conditions that includes high blood sugar levels, high triglycerides, low levels of HDL (the “good” cholesterol), and too much fat around the waist.

For this placebo-controlled, double-blind clinical study, the women were randomly assigned to take either 4,000 IU of vitamin D3 or an inactive placebo each day. Then, at the end of six months, the scientists examined the research subjects’ health profiles. The results showed significant improvements in the vitamin D group. Specifically, their insulin resistance dramatically improved with a decrease in their fasting insulin levels. This slashed the risk they would go on to develop diabetes.

When the study began, the women’s vitamin D levels were about 50 nanomoles per liter (nmol/L), close to the average level of vitamin D (60 nmol/l) in US men and women. The researchers found that health effects were optimal when the women’s blood levels of vitamin D reached between 80 to 119 nmol/L — far higher levels than those of the typical American. In fact, the documented low levels of vitamin D in the US population could explain why 70 to 80 million Americans now have pre-diabetic metabolic syndrome, according to National Institutes of Health statistics.

The Massey University study backs up other research published earlier this year in the Diabetic Medicine journal. A team of Indian scientists from Sitaram Bhartia Institute of Science and Research in New Delhi found that even a short-term large dose of vitamin D3 supplementation had a positive impact on insulin sensitivity in 71 apparently healthy, middle-aged men with “spare tires” around their bellies — the central obesity associated with the pre-diabetes metabolic syndrome. Taking vitamin D3 improved their postprandial (after a meal) insulin sensitivity, lowering their risk of developing diabetes down the road.